The present invention relates to a plasma display apparatus that uses a plasma display panel (PDP).
A plasma display panel (referred to as a PDP hereinafter) has recently attracted interest as a display device that can be used as a wall-mounted television, and so on. Since the plasma display apparatus that uses a PDP has been disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-272182, a detailed description is omitted here and only the assembly structure of a plasma display apparatus that directly relates to the present invention is described.
FIG. 1 is an exploded perspective view that shows the assembly structure of a plasma display apparatus, FIG. 2 is a perspective view that shows an assembled plasma display apparatus, and FIG. 3 is a partially sectional view of the assembled plasma display apparatus. In the drawings, reference number 1 refers to a PDP, 2 refers to a chip tube to draw off the gases in the PDP, 3 refers to a main frame, 5, 6, and 7 refer to circuit substrates that mount drive circuits, and so on, and 4 and 8 refer to drivers.
The PDP 1 is basically composed of a pair of glass substrates. Because of this, it is difficult to use devices such as screws to directly fix the circuit substrates 5, 6 and 7 onto the PDP 1 and, therefore, another method is employed in which the circuit substrates 5, 6, and 7 are fixed onto the main frame 3 composed of a metal plate, and so on, and then this main frame 3 is bonded and fixed to the PDP 1 with adhesive tape such as a double-sided tape.
The main frame 3 to be bonded to the PDP 1 is required to distribute and radiate the heat generated in the PDP 1 evenly. Because of this, the main frame is composed of materials of a high heat conductivity and is engineered with an increased surface area to provide a better function as a heat sink.
On the other hand, strips of adhesive tape 10 are spaced equally between the main frame 3 and the PDP 1. More concretely, for example, after strips of the adhesive tape 10 are fixed to the entire surface of the PDP 1, side by side, the main frame 3 is fixed, but it is possible the PDP 1 is fixed after the adhesive tapes 10 are fixed to the main frame 3. The adhesive tape 10 is made of materials of a high heat conductivity and serves to transfer the heat generated in the PDP 1 to the main frame 3.
When the adhesive tape 10 is fixed to the PDP 1 or the main frame 3, or when the PDP 1 or the main frame 3 is fixed to the already fixed adhesive tape 10, a problem is caused in that air is enclosed therebetween and air bubbles are prone to form. Air bubbles form an air layer and prevent heat from being transferred and, therefore, it is necessary to remove air bubbles between the adhesive tape 10 and the PDP 1 and between the adhesive tape 10 and the main frame 3 when fixed to each other in order to utilize the heat conductivity of the adhesive tape 10 sufficiently. Therefore, work to draw off the air bubbles was performed in the conventional assembly process. The work to draw off the air bubbles is, however, not easy to carry out and a problem is caused in that the air bubbles are not removed sufficiently and the manufacturing costs are increased.
To solve these problems, Japanese Unexamined Patent Publication (Kokai) No. 10-254372 has disclosed a structure in which recesses and projections are provided on the surface, in contact with the PDP, of the heat conduction sheet interposed between the PDP and the frame chassis (main frame).
The air layers remain not only on the contact surface between the heat conduction sheet and the PDP but also between the heat conduction sheet and the main frame, and both have the same influence on the conduction of heat from the PDP to the main frame. Japanese Unexamined Patent Publication (Kokai) No. 10-254372, however, only refers to elimination of the air layers on the surface, in contact with the plasma display panel, of the heat conduction sheet, not to the air layers on the surface, in contact with the main frame, of the heat conduction sheet. In the invention disclosed in Japanese Unexamined Patent Publication (Kokai) No. 10-254372, air is drawn off through the space between the recesses and the projections during fixing, but the space provided is small and it is actually difficult to draw off air completely through the space.
Moreover, since the PDP 1 is composed of glass substrates, it will be indispensably necessary to ensure strength when the size is enlarged. Because it is difficult to employ the main frame 3 that is intricate and expensive, however, the conventional main frame 3 was composed of a thin metal plate. Therefore, if the circuit substrates 4, 5, 6, 7, and 8 are just mounted onto the main frame 3, a problem is caused in that the strength of the plasma display apparatus is not sufficient. In order to improve the rigidity, it may be necessary, for example, to increase the thickness of the main frame 3 or add reinforcing parts. When increasing the thickness of the main frame 3, however, it is required to increase the degree of flatness of the main frame 3, and a problem, that costs are increased, occurs. In other words, if the main frame 3 is warped, it is adjusted to the PDP 1, and if the main frame 3 is thin, the load to the PDP 1 is small and this does not cause a serious problem. If the main frame 3 is thick, however, the PDP 1 bonded to the warped main frame 3 receives an excessive load, and cracking of the panel may occur.
It is preferable that the surface area of the main frame 3 is large enough to increase the heat radiation efficiency. Therefore, a large heat sink with a large surface area is conventionally used as a reinforcing part, but this causes a problem in that the cost of the reinforcing parts is increased.